I collected my 'new' 2015 C3 Picasso Exclusive 1.6 BlueHdi today and soon noticed a low frequency humming/booming sound, which to my ears was quite loud. It is apparent at low speed and with the clutch disengaged. It doesn't stop when I touch the brakes.
I drove about ten miles towards home before I made my mind up that it just didn't seem right, so drove back to the dealership, Aston Vauxhall at Melton Mowbray. I went out in the car with the same mechanic who had just serviced it and although I could still here it, Sod's Law dictated that it didn't seem quite as loud (I wondered if the extra person in the passenger seat altered the internal sound characteristics a bit). It had just been serviced and MOT'd, so he suggested that the most likely cause was tyre noise. It has Michelin Eco tyres on the back and some decent quality cheaper tyres on the front.
I'm sure they were being quite genuine and not trying to fob me off in any way, but I wondered if my hearing was just better than theirs, because it was still very obvious to me. So, the question is, has anybody else experienced similar? The noise doesn't change with speed, as I thought it would with anything wheel related. Any ideas?